1. Technical Field
The present invention relates to an optical waveguide, a package board having the optical wave guide, and methods of manufacturing thereof.
2. Description of the Related Art
With the recent developments in computers and communication technology, the transfer speed of signals has become an important parameter. Accordingly, impedance matching between the components and the wiring is becoming important in a high-frequency package board.
The package board used a conductive metal such as copper, etc., for the electrical wiring, as a medium for the transfer of signals, there was a limit to transmitting data at ultra-high speeds and in high capacities. As a method of overcoming this problem, the optical package board was developed, in which an optical waveguide of a particular size is formed directly in a silicon substrate, which is then mounted on a package board.
That is, in the past, the method used in manufacturing a package board included forming circuit patterns on a copper plate to form the inner and outer layers of a package board, but recently, the method is being used of inserting in the package board an optical waveguide, which is capable of exchanging signals by light using polymers and glass fibers.
Here, an optical waveguide refers to a means for transmitting optical signals that consists of a center portion having a high refractive index, known as the core, and a surrounding portion having a low refractive index, known as the cladding. When an optical signal enters such an optical waveguide, the incident optical signal undergoes repeated total reflection at the boundary between the core and cladding, which allows the optical signal to travel through the core.
The materials for optical fibers include glass fibers and plastic fibers, where glass fibers can be subdivided into quartz type glass fibers and multi-element glass fibers. For communication uses, quartz type glass fibers are mainly used, which provide lower losses, while plastic fibers are commonly used for transmitting light energy, as lighting devices or decorations.
A typical manufacturing method for an optical waveguide includes the stacking-type method, in which the core is formed over a lower cladding layer, after which the core is processed to form an inclined surface, and then an upper cladding layer is formed.
With this method, however, a separate dicing process may be required, in order to form the inclined surface which alters the paths of optical signals. Moreover, in cases where several inclined surfaces are to be formed, the dicing process may be repeated a corresponding number of times, greatly degrading production efficiency.